An H II region beyond the optical disk of the galaxy

The supergiant H II region 30 Doradus is placed in context as the optically most spectacular component in a much larger region of recent and current star formation in the Large Magellanic Cloud, as shown by deep Hα photographs and the new IRAS results. The current state of knowledge concerning the concentrated central cluster in 30 Dor is summarized. Spectroscopic information exists for only 24 of the brightest members, most of which are WR stars; however, photometry shows over 100 probable members earlier than BO. The spectral classification of these stars is a difficult observational problem currently being addressed; in the meantime their hypothetical ionizing luminosity is calculated from the photometry and compared with that suggested for the superluminous central object R136a alone, and with the H II region luminosity. With reference to related regions in the Galaxy, the likelihood that many of the brightest objects in 30 Dor are multiple systems is emphasized. An interpretation of R136a as a system containing a few very massive stars (as opposed to a single supermassive object) is in good accord with the observations, including the visual micrometer results. The study of 30 Dor and its central cluster is vital for an understanding of the numerous apparently similar regions now being discovered in more distant galaxies.

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Galactic starburst NGC 3603 from X-rays to radio

Symposium - International Astronomical Union ◽

10.1017/s0074180900212710 ◽

2003 ◽

Vol 212 ◽

pp. 515-522

Author(s):

Anthony F.J. Moffat ◽

Keyword(s):

Mass Function ◽

Initial Mass Function ◽

X Rays ◽

Stellar Content ◽

Near Ir ◽

The Galaxy ◽

The Status ◽

H Ii Region ◽

Mass Segregation ◽

Colliding Winds

While NGC 3603 is often quoted as the most massive visible Giant H ii Region in the Galaxy, there are other similar and even more massive regions now being found towards the inner Galaxy in the near-IR. Nevertheless, NGC 3603 still retains the status of clone to the dense core-object in 30 Dor, R 136 — but 7x closer and 49x less crowded! This paper summarizes the most recent findings concerning NGC 3603's color-magnitude diagram (CMD), initial mass function (IMF), mass segregation and stellar content — including its unusually luminous H-rich WNL members — down to its pre-main-sequence stars near the H-burning limit. Of special relevance are new high-resolution X-ray and radio images as related to merging/colliding winds and three massive proplyd-like objects. NGC 3603 is a somewhat younger, hotter, scaled-down version of typical starbursts found in other galaxies.

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How to Model the Chemical Evolution of Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900172407 ◽

1993 ◽

Vol 155 ◽

pp. 557-566

Author(s):

Joachim Köppen

Keyword(s):

Star Formation ◽

Chemical Evolution ◽

Time Scale ◽

Life Time ◽

Magellanic Clouds ◽

Formation Time ◽

List Type ◽

The Galaxy ◽

H Ii Region ◽

Magellanic Stream

For a first interpretation of the comparison of observational data, the crude “Simple Model” of chemical evolution is quite useful. Since it has well been described in the literature (e.g. Pagel and Patchett 1975, Tinsley 1980), let us here just review the assumptions and whether they are satisfied: 1.The galaxy is a closed system, with no exchange of matter with its surroundings: For the solar neighbourhood this probably is not true (the infamous Gdwarf-“problem”, Pagel 1989b). For the Magellanic Clouds this is most certainly wrong, because of the presence of the Inter-Cloud Region and the Magellanic Stream, and evidence for interaction with each other and the Galaxy as well (cf. e.g. Westerlund 1990).2.It initially consists entirely of gas (without loss of generality of primordial composition): This is good approximation also for models with gas infall, as long as the infall occurs with a time scale shorter than the star formation time scale.3.The metal production of the average stellar generation (the yield y) is constant with time: Initially, it is reasonable to make this assumption. For tables of the oxygen yield see Koppen and Arimoto (1991).4.The metal rich gas ejected by the stars is completely mixed with the ambient gas. To neglect the finite stellar life times (“instantaneous recycling approximation”) is appropriate for elements synthesized in stars whose life time is much shorter than the star formation time scale, such as oxygen, neon, sulphur, and argon.5.The gas is well mixed at all times: We don't know. The dispersion of H II region abundances may give an indication. In the Magellanic Clouds Dufour (1984) finds quite a low value (±0.08 dex for oyxgen).

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Massive Star Formation in W49

Symposium - International Astronomical Union ◽

10.1017/s0074180900095152 ◽

1987 ◽

Vol 115 ◽

pp. 143-145

Author(s):

J. Dreher ◽

S. Vogel ◽

S. Terebey ◽

W. J. Welch

Keyword(s):

Star Formation ◽

High Resolution ◽

Massive Star ◽

Hii Regions ◽

Molecular Line ◽

The Galaxy ◽

Molecular Lines ◽

H Ii Region ◽

Scale Structures ◽

The Continuum

W49 is the most luminous H II region complex in the galaxy. VLA maps in the continuum reveal a complex of more than two dozen compact HII regions, including a ring-like distribution of a dozen such regions within a volume of 1 pc. In addition to the VLA maps, we have obtained high resolution maps in this field with the Hat Creek Millimeter Interferometer in the following molecular lines: HCO+(1-0), H13CO+(1-0), SiO(v = 0, J = 2-1), SiO(v = 1, J = 2-1), H13CN(1-0), HC15N(1-0), SO2 [8(3,5)-9(2,8)], SO2[8(1,7)-8(0,8)], SO[2(2)-1(1)], and CH3CH2CN[10(1,10)-9(1,9)], all near 3 mm wavelengh. These maps will be discussed. The HCO+distribution corresponds to the larger scale structures observed in the continuum maps. In contrast the SO and SiO sources are quite compact. Using the detailed molecular line results obtained in the ORION/KL region as a guide, we are able to identify these latter sources as regions in which the star formation is at an earlier stage, regions where there are outflows.

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Bar effect on gas-phase abundance gradients. I. Data sample and chemical abundances

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2246 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2359-2379 ◽

Cited By ~ 1

Author(s):

A Zurita ◽

E Florido ◽

F Bresolin ◽

E Pérez-Montero ◽

I Pérez

Keyword(s):

Emission Line ◽

Gas Phase ◽

Direct Method ◽

Structural Parameters ◽

Companion Paper ◽

Strong Line ◽

H Ii Regions ◽

Chemical Abundances ◽

The Galaxy ◽

H Ii Region

ABSTRACT Studies of gas-phase radial metallicity profiles in spirals published in the last decade have diminished the importance of galactic bars as agents that mix and flatten the profiles, contradicting results obtained in the 1990s. We have collected a large sample of 2831 published H ii region emission-line fluxes in 51 nearby galaxies, including objects both with and without the presence of a bar, with the aim of revisiting the issue of whether bars affect the radial metal distribution in spirals. In this first paper of a series of two, we present the galaxy and the H ii region samples. The methodology is homogeneous for the whole data sample and includes the derivation of H ii region chemical abundances, structural parameters of bars and discs, galactocentric distances, and radial abundance profiles. We have obtained O/H and N/O abundance ratios from the Te-based (direct) method for a subsample of 610 regions, and from a variety of strong-line methods for the whole H ii region sample. The strong-line methods have been evaluated in relation to the Te-based one from both a comparison of the derived O/H and N/O abundances for individual H ii regions and a comparison of the abundance gradients derived from both methodologies. The median value and the standard deviation of the gradient distributions depend on the abundance method, and those based on the O3N2 indicator tend to flatten the steepest profiles, reducing the range of observed gradients. A detailed analysis and discussion of the derived O/H and N/O radial abundance gradients and y-intercepts for barred and unbarred galaxies is presented in the companion Paper II. The whole H ii region catalogue including emission-line fluxes, positions, and derived abundances is made publicly available on the CDS VizieR facility, together with the radial abundance gradients for all galaxies.

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Hα19 in the galaxy M 33, a high-luminosity massive merging eclipsing binary

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311011549 ◽

2010 ◽

Vol 6 (S272) ◽

pp. 610-611

Author(s):

Vitaly P. Goranskij ◽

Elena Bersukova

Keyword(s):

Absorption Line ◽

Orbital Period ◽

Accretion Rate ◽

Hot Spot ◽

Line Spectrum ◽

High Luminosity ◽

Ccd Photometry ◽

Eclipsing Binary ◽

The Galaxy ◽

H Ii Region

AbstractCCD photometry reveals a hot spot on the surface of the hot accretion gainer in this supergiant O type binary with a big accretion rate. This spot is as bright as 25000 Suns. The orbital period of this system is 33.108 days. The absorption-line spectrum contains multiple lines of He I, Si III and N II. The star is associated with H II region formed by bipolar gas outflow from the system.

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Molecular gas and star formation beyond the optical disk of the galaxy

Lecture Notes in Physics - The Physics and Chemistry of Interstellar Molecular Clouds ◽

10.1007/bfb0102085 ◽

1995 ◽

pp. 30-32

Author(s):

E. J. de Geus ◽

S. W. Digel

Keyword(s):

Star Formation ◽

Optical Disk ◽

Molecular Gas ◽

The Galaxy

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The stellar content of NGC 3603

Symposium - International Astronomical Union ◽

10.1017/s0074180900205950 ◽

1999 ◽

Vol 193 ◽

pp. 403-411

Author(s):

Laurent Drissen

Keyword(s):

Main Sequence ◽

Stellar Content ◽

The Galaxy ◽

H Ii Region ◽

Low Mass

At the heart of the galactic giant H II region NGC 3603, low-mass (1–4 M⊙) stars slowly contract toward the main sequence, while peacefully cohabiting with the three most luminous, hydrogen-rich Wolf-Rayet stars in the Galaxy, a dozen hot O3–4 stars and their more modest but numerous O and B companions. This is the story of a very young and dense starburst cluster …

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